A flash smelting process takes place in a flash smelting furnace that consists of three sections: a reaction shaft, a lower furnace, and an uptake. In the flash smelting process, a pulverous concentrate mixture that consists of sulphidic concentrates, fluxes, and other pulverous components, is mixed with a reaction gas by means of the concentrate burner in the upper part of the reaction shaft. The structure of the concentrate burner plays a radical role in the proper functioning of the flash smelting process. The reaction gas can comprise air, oxygen-enriched air or oxygen. The concentrate burner comprises a number of concentric channels, through which the reaction gas and the concentrate are blown to and mixed in the furnace. Concentrate burners are known previously, for example, from publications FI 98071 B and FI 100889 B. This burner, known as the Outokumpu burner, comprising separate channels for the pulverous solid matter, such as concentrate, and flux, and process gas, is globally the most widely used burner in flash smelting furnaces. The concentrate burner includes a feeder pipe, its orifice opening to the reaction shaft for feeding the pulverous matter to the reaction shaft. It is preferable to use air or part of the reaction gas as a dispersing gas, and to feed it from the inside of the feeder pipe along a dispersing pipe. The upper surface of the lower part of the dispersing pipe is designed so as to be outwards curved and its lower edge is provided with holes that are directed to the side, through which the reaction gas is fed essentially horizontally towards the pulverous solid matter falling downwards. The dispersing pipe is arranged concentrically inside the feeder pipe and it extends to a distance from the orifice inside the reaction shaft for directing the dispersing gas to the concentrate powder flowing around the dispersing pipe. The main part of the reaction gas is fed into the reaction shaft through a gas supply device. The gas supply device includes a reaction gas chamber, which is outside the reaction shaft and opens to the reaction shaft through an annular discharge orifice that concentrically surrounds the central feeder pipe for mixing the reaction gas discharging from the discharge orifice with the flow of pulverous matter that runs from the feeder pipe by means of gravity and is directed sideward by means of the dispersing gas. The main purpose of the concentrate burner is to provide an optimal suspension of the solid particles and the reaction gas in the reaction shaft. Individual particles are heated and, after ignition, they begin to burn with the oxygen that is in the reaction gas. Combustion reactions with fine sulphides are quick and an essential amount of heat is released, resulting in a perfect melting of the concentrate mixture particles and the other solid matters in the feed mixture. The melted particles flow downward and accumulate in the lower furnace, where slag and the sulphidic matte settle into separate layers. The combustion gas (mainly a mixture of SO2 and N2) flows through the uptake to a waste heat boiler, where its heat is recovered.
Publications CN 2513062Y and CN 1246486C disclose a concentrate burner, wherein the reaction gas chambers that are arranged within each other are formed into turbulent flow chambers to provide a turbulent flow of the reaction gas discharging from the discharge orifice. Each reaction gas chamber includes a cylindrical upper part, to which an inlet channel opens tangentially for conducting the reaction gas to the interior in a tangential direction, and a conical lower part, which converges conically from the cylindrical upper part down towards the discharge orifice. With this arrangement, the reaction gas can be made to swirl in the reaction gas chamber, where it exits swirling from the discharge orifice to the reaction shaft.
One problem with the known concentrate burner is that there is no way of adjusting the amount of turbulence. The turbulence can ignite an excessively effective flame too quickly, causing problems to the middle part of the shaft.